A laptop computer may be connected...
A laptop computer may be connected to the ECU using this wiring harness. When not in use, the harness is removed and is not visible under the glovebox.
After all the parts were installed, it was time to try an initial start-up. Without proper tuning, the engine would start and run for a few seconds before dying, just as the FAST manual predicted. After several online calibration sessions to change the ECU settings, the car was ready for a testdrive. It was immediately apparent that a very lean condition existed, and numerous additional data-logging sessions were required before the mixture was correct.
During the various data-logging runs, another huge problem surfaced. Fuel in the vapor separator tank continued to flow out of the vent line, especially when the engine temperature was high. The MerCruiser VST was designed to operate under pressure, and we were attempting to make it work with a vent system only. After many changes to the VST vent system with no positive results, it was time to look for other solutions.
I decided to call Brett Clow at Aeromotive, who had helped me select a fuel-pressure regulator early in the build process. After a few calculations, Brett determined that the small amount of fuel being recycled in the VST was getting very hot due to the 45-pound regulated pressure, possibly vaporizing fuel. He suggested I run a return line to the gas tank to cool the fuel, something I had hoped to avoid.
I informed Craig of this idea, and he immediately called Brett to discuss other possible solutions. After some debate, the two recommended I try cooling the fuel through a transmission-oil cooler. Based on a call to Derale Cooling Products, I selected a heavy-duty trans cooler (PN 13303). This cooler utilizes -6AN ports, the same size I adapted to the VST. The cooler was mounted in front of the radiator and plumbed to the pressure regulator and return line in the VST.
A subsequent testdrive bore out the system's merits. Fuel temperatures were reduced by about 20-degrees F, and there was no discharge from the VST vent line. Problem solved!
Next, Craig suggested I bring the car to BDS for a final ECU-calibration session. I expected to make a few test runs to get the computer dialed-in, but the process proved to be much more involved. We made multiple runs together in the car, with Craig fine-tuning the electronics on his laptop during and after each run. He then sent me out to drive the car as normal, allowing him to obtain a data log under real-world conditions. Craig revised the fuel map after each run until the tuning was fully dialed-in.
Did we mention that all this...
Did we mention that all this cool fuel-injection stuff was attached to a pretty cool '65 roadster? Check out our Feb. '04 issue for more info on this Vortech-blown midyear.
This conversion was a challenging, and at times, frustrating project, but the end result has proved well worth the effort. Thanks to a little hard work and some engineering creativity, this classic roadster now boasts all the performance and drivability of its late-model counterparts.
Author's note: On Craig's recommendation, I have since replaced the original AC fuel pump, which pumps at 7.5 psi, with an Aeromotive pressure regulator (PN 13201) installed between the pump and the VST. I limit the pressure to 6 psi, and the system works fine at that setting.
The author would like to thank Craig Railsback, Blower Drive Service; Brett Clow, Aeromotive; Tom Marquez, M&H Electric Fabricators; Leon Derebery, Derebery Performance Marine; Joe Lapille, Autotronic Controls; and Craig Smith, ACCEL (a Mr. Gasket Company).
Rochester FI plenum (PN 7017380) and cover
FAST ECU (PN 30-11701)
MerCruiser vapor-separator tank (PN 806787A3)
ACDelco 75mm throttle body (PN 863078A06 or 863379A06)
Magneti Marelli 45-pound fuel injectorsAeromotive pressure regulator (PN 13105)
Aeromotive pressure regulator (PN 13201; fits between mechanical fuel pump and VST)
ACCEL DFI distributor (PN 77110)
MSD 6A ignition (PN 6200)
MSD coil (PN 8202)
BDS 2-bar MAP sensor (PN 56602)
BDS water-temp sensor (PN 56610)
BDS air-temp sensor (PN 56620)
MSD 8mm plug wires (PN 3123)
Derale heavy-duty fluid cooler (PN 13303)
Misc. #16 and #14 primary wire
Misc. weatherpack connectors and pins
Stainless-steel seamless tubing, 3/16-inch and 3/8-inch
Misc. stainless AN fittings
Misc. 303 stainless bar stock